Discussion

Mid-aortic syndrome is an uncommon vascular disorder characterised by stenosis of the lower thoracic or abdominal aorta. Despite its low incidence, poor prognosis and high mortality have been reported in infantile mid-aortic syndrome with refractory hypertension. ^{Reference Rumman, Nickel and Matsuda-Abedini1,Reference Forman, Sinskey and Shalabi2} Mid-aortic syndrome-related diseases may include genetic disorders such as neurofibromatosis-1, Williams syndrome, and Alagille syndrome, as well as inflammatory disorders like Takayasu’s arteritis, which can cause arterial stenosis. Nonetheless, the aetiology of idiopathic mid-aortic syndrome remains largely unknown. ^{Reference Lazea, Al-Khzouz and Sufana3} Mid-aortic syndrome is usually diagnosed by CT angiography or MR angiography, which shows diffuse or segmental stenosis of the abdominal aorta. ^{Reference Hirsch and Hong7} Additional classification can be made based on location and severity of aortic stenosis in aorta and its major arterial branches. ^{Reference Musajee, Gasparini, Stewart, Karunanithy, Sinha and Sallam4,Reference Delis and Gloviczki8} In general, medical therapy, endovascular procedures, and surgical options are considered for the treatment of mid-aortic syndrome. Establishing a standard of management protocol for mid-aortic syndrome patients is challenging due to the rarity of the disease and the limited available evidence. However, it is evident that patients with poorly controlled blood pressure or worsening heart failure, despite appropriate medical therapy, benefit from invasive managements, including endovascular intervention and open surgical repair. ^{Reference Forman, Sinskey and Shalabi2,Reference Delis and Gloviczki8,Reference Chalmers, Dhadwal, Deal, Sever and Wolfe9} Most reported cases of infantile mid-aortic syndrome involved with severe aortic stenosis that required interventional treatment. ^{Reference Zhao, Zhu and Zhao5,Reference Thompson, Sprouse, Mir and Burkhart10} Additionally, idiopathic mid-aortic syndrome often leads to refractory hypertension necessitating invasive options. ^{Reference Rumman, Nickel and Matsuda-Abedini1,Reference Musajee, Gasparini, Stewart, Karunanithy, Sinha and Sallam4} However, in neonatal or infant patients, endovascular or surgical intervention can be demanding due to the lack of consensus on indications for invasive approaches, the small size of the vessels, the high risk of operative or anaesthetic complications, or inoperability. According to a recent review by Rumman et al., 14.4% of patients became normotensive, and 35.8% showed improvement with conservative medical treatment. ^{Reference Rumman, Nickel and Matsuda-Abedini1} Given the sufficient outcome of medical treatment in cases with mild-to-moderate stenosis, appropriate medical management can be important and beneficial, especially for neonates or infants. In our case, a 2-month-old patient was initially diagnosed with heart failure associated with dilated cardiomyopathy. When investigating her birth history, she was born at 40 weeks and 5 days of gestation with a birth weight of 3.56 kg via caesarean section. In other words, there were no notable perinatal conditions aside from the caesarean delivery, and she had no significant medical issues until her first visit to our hospital. There is no history of any intra-arterial catheterisation, particularly umbilical arterial lines. She presented with cough and respiratory distress as her primary manifestations but did not initially exhibit definite hypertension. After admission to our paediatric ICU, she also experienced intermittent oliguria requiring proper diuretic supports and apparent hypertensive blood pressure in the upper extremities, despite decreased cardiac function, which provided clues for a diagnosis of mid-aortic syndrome. Although the blood pressure difference in her four extremities appeared mild, our prior experience with another patient who had mid-aortic syndrome and exhibited a similar blood pressure discrepancy led us to perform CT angiography for her whole abdomen to rule out mid-aortic syndrome aggressively. During the course of her treatment, the patient did not show other well-known causes of mid-aortic syndrome, such as the previously mentioned congenital or acquired disorders, nor did the CT imaging show evidence of external compression from any adjacent mass-like lesion. Therefore, we suspected that the most likely cause of mid-aortic syndrome in this patient was idiopathic. Thankfully, in our patient, a trial of medical management as the first-line approach for hypertension and heart failure was sufficient. Moreover, there was a radiologically confirmed spontaneous relief of her mid-aortic syndrome without any invasive intervention during follow-up. Our case emphasises the rare disease course of mid-aortic syndrome in infancy, presenting cardiomyopathy and heart failure. Despite the young diagnostic age and idiopathic cause, the significant narrowing of the abdominal aorta showed interval regression while our patient received consistent medical treatment. This indicates effective management of the systemic effects caused by mid-aortic syndrome through medication, allowing the patient to achieve stable conditions supportive of sufficient growth and natural recovery. Consequently, this resulted in the spontaneous normalisation of the abdominal aortic narrowing.